Hitherto, there have been generally used a thread-wound golf ball and a solid golf ball. A thread-wound golf ball is made by winding a rubber thread around a liquid center or solid center, and then covering the wound center with a balata (i.e., trans-polyisoprene) or ionomer-based resin. A solid golf ball, such as a two- and three-piece golf ball, has a rubber core and a resin cover made of a thermoplastic resin such as ionomer resin. Comparing with a thread-wound golf ball, a solid golf ball can attain a longer flying distance due to a higher initial speed of the ball by a shot of a golf club. In addition, the solid golf ball is better in durability. On the contrary, the solid golf ball generally has a higher hardness, thus receiving a large impact at shooting. Furthermore, the solid golf ball makes it difficult for the player to impart intentional spin and therefore it has a poor controllability especially at an approach shot. Because of these reasons, the solid golf ball has not been positively used by skilled golfers such as professional golfers and senior amateur golfers to whom excellent shot feeling and controllability is beneficial.
To improve the shot feeling and controllability of a solid ball, a variety of improvements have been made by adjusting the hardness of a cover, the hardness of a core and/or the hardness distribution thereof. For example, Japanese Unexamined Patent Publication No.9-239067 discloses a two-piece solid golf ball which includes a solid core having a specified hardness distribution for a surface, a center and a point at 5 mm inside from the surface; a cover having a specified hardness and thickness; and a specified number of dimples.
However, the shot feeling and controllability of a solid golf ball have not been improved without decreasing a flying distance and durability of the ball. Therefore, further improvements has been demanded to solve the problem.